Could Delayed Periods Be Due To Stress?

Hi Im 19 years old. I lost my virginity last October 8 - that was my last day of period. I wasn't so sude about my first day but probably around 3 or 4 too. Since then, I began to be conscious about my menstrual cycle. My next period came Nov 4-8 and then Dec 3-8. It was only last month that we were sexually active wherein Dec 10 - condom (no breaking and was worn the whole time), Dec 13 - Pull out, Dec 20 - condom (no breaking and was worn the whole time), Dec 27 - pull out (Quick and once) and Dec 31 - condom (no breaking and was worn the whole time). I was expecting to have my period last Jan 3 but Im now 6 days late. I took a PT on my 4th day late of period and 5th, both turns out to be negative. I honestly think I'm not pregnant since we were safe even during the pull out, we ensured there was no pre cum n everything was clean before we did it. He came 2-3x. Is there a possibility I can be pregnant? I don't feel anything and my breasts arent sore. Although Im having small vaginal discharges which could mean my period is fast approaching. All my friends think who are more sexually active than me, that Im just stressed out and irregular period. Am I really irregular? When should I take my next PT?